Darius the Great

Darius the Great (550 BC-486 BC) was the King of Persia from 522 BC to 486 BC, succeeding Bardiya and preceding Xerxes I of Persia. His quelling of Greek rebellions in Ionia led to the Greco-Persian Wars, during which his invasion force was defeated at the Battle of Marathon in 490 BC. He died during a campaign in Egypt in 486 BC.

Biography
Darius was the son of Satrap Hystaspes of Bactria and Rhodugune, and he became the personal lancer of King Cambyses II of Persia. In 522 BC, he overthrew the usurper Gaumata and quelled several rebellions across the Persian Empire, rising to become the new Emperor. During the 490s BC, the Ionian Revolt broke out among the Ionian Greeks of Asia Minor, and Darius crushed the uprisings before preparing a punitive expedition against Athens and Eretria for their support of the revolt. In 490 BC, the invasion force was defeated at the Battle of Marathon, but Darius succeeded in re-subjugating Thrace, conquering Macedon, annexing the Cyclades and the island of Naxos, and sacking Eretria. Darius would reorganize the empire into satrapies and appointed satraps to govern them, and he created a coinage system, made Aramaic the official language of the empire, built roads and introduced standard weights and measures, worked on construction projects, and centralized and unified the empire. He died in 486 BC while campaigning against a revolt in Egypt, and his son Xerxes I of Persia undertook another invasion of Greece in 480 BC.